How about this example sentence fragment? "to explore strange new worlds, to seek out new life and new civilizations, to boldly go where no man has gone before." The "to"s are not required but add a certain dramatic emphasis, rhythm and, I think, a suggestion that it's not a prioritized list but are all equal goals.
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WudangNov 20 '11 at 17:06

I'm saying I'm confused. "Learn" requires a to-infinitve construct (I wrote the wrong gerund form here, sorry), it should be "...learn to apply theories to...", I think. If I understand your sentence correctly, though, then "to" isn't necessary after each comma. In fact, it is correct to say: "Working in the field helps us learn to apply theories...", ie help + bare infinitive if your sentence is in informal context.
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IreneNov 20 '11 at 17:10

It's an awkward sentence with all the gerunds, but I wouldn't call it incorrect English. I would change this part at least, "...to learn how to apply theories to solving..."
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mkennedyNov 20 '11 at 17:17

2 Answers
2

As was suggested by Wudang, the parallel structure of the phrases helps draw them together. Often parallel sections of a sentence are introduced by a single word in the main part of the sentence, but in this case repeating the common word certainly makes it easier to follow. I assume that your intent was to have parallel sections as this:

Working in the field helps us to learn how to apply theories
to solve real-world problems,
to apply […], and
to […].

The only problem is that you have the word 'to' in other places that might make it difficult to separate out which are part of the parallel structure and which are not, as this:

Working in the field helps us
to learn how [something works]
to apply theories
to solve real-world problems,
to apply […], and
to […].

The first one obviously doesn't fit the pattern (as is), but the rest seem as though they could be parallel. If your intent is to focus only on those last three (and any additional ones), then you might reword the beginning to avoid the wordiness as:

Working in the field teaches us
to apply theories
to solve real-world problems,
to apply […], and
to […].

In this case each of the parallel phrases correctly completes the introductory phrase, and the repeated word 'to' pulls the reader through, allowing a pause just before each section.

The alternate method would be to use the connecting word once as:

Working in the field teaches us to
apply theories
solve real-world problems,
apply […], and
[…].